In order to improve the yield of semiconductor products, it is important for process improvements to detect a defect in a manufacturing process at an early stage in an analysis to evaluate how the process has been completed.
TEM electron beam diffraction, EELS, and EDX analysis have heretofore been used to analyze the crystallinity and composition of a given layer in a sample. However, these analysis methods are destructive analyses that require the sample to be processed into flakes, and are therefore unsuitable for line monitoring. Raman spectroscopy is an evaluation method that does not necessarily require the sample processing, and can obtain a Raman peak corresponding to the crystal structure of an analysis target layer. Therefore, the Raman spectroscopy is a technique that is effective in the nondestructive line monitoring.
The Raman spectroscopy requires a laser light source which excites molecular vibration. Since the penetration depth into a sample to be measured is determined depending on the wavelength of a laser light, it is necessary to select a wavelength in accordance with the depth of a target layer when a structure is evaluated. When a sample is a semiconductor device having a stack structure and is evaluated in the direction perpendicular to its upper surface, information that can be obtained in the depth direction varies by a laser wavelength to be selected.
The above-mentioned conventional evaluation method is effective when the number of stacked layers in the structure is small. However, for example, as in a three-dimensionally stacked semiconductor storage device, the number of stacked layers in a structure has been increasing in recent years. Even a single layer may be increasing in thickness. It has been increasingly difficult to extract information at a desired layer in the multilayer structure and information at a position of an arbitrary depth in thick layers.